Skin-to-skin contact improves sleep stability in preterm infants.

BACKGROUND: Sleep supports neurophysiological maturation in preterm infants, yet the impact of developmental care interventions on sleep remains poorly quantified. Skin-to-skin contact (SSC) improves physiological stability, but its effects on sleep structure measured with automated methods are unclear. We hypothesized that SSC increases sleep duration and reduces sleep fragmentation. METHODS: In this prospective observational study (September 2024-May 2025), clinically stable preterm infants born at 29 + 0 to 33 + 6 weeks' gestation were enrolled in a level III Neonatal Intensive Care Unit. Infants with major congenital anomalies or recent exposure to sedatives or analgesics were excluded; caffeine therapy was allowed. Each infant received ≥1 hour of SSC. Cardiorespiratory monitoring data were analyzed using a validated machine-learning algorithm to classify sleep states across three hour-epochs: before, during, and after SSC. Primary outcomes were sleep-state proportions and approximate entropy (ApEn). RESULTS: 61 infants contributed to 91 recordings. SSC shifted the wake-sleep balance toward sleep dominance. ApEn decreased after SSC, indicating greater regularity and stabilization of sleep-wake transitions. Higher gestational age was independently associated with lower ApEn, consistent with maturational stabilization of sleep architecture. CONCLUSION: SSC is associated with more continuous and stable sleep in preterm infants. Automated physiologic monitoring provides a non-invasive method to quantify developmental care effects and may offer sensitive markers of neurophysiological regulation. IMPACT STATEMENT: Skin-to-skin contact in preterm infants is associated with less wakefulness and reduced sleep fragmentation, with effects persisting beyond the period of contact, indicating a more stable sleep-wake organization. The study provides quantitative evidence that skin-to-skin contact influences sleep organization in preterm infants, demonstrating effects not only during the intervention but also in the subsequent period. These findings strengthen the physiological rationale for skin-to-skin contact by showing that it supports more stable sleep, a central behavioural state linked to early brain development in preterm infants.